_.isNative(value)
147
_.isNative(value)
_.isNative检查一个值是否是原生function
注意:这个方法在core-js包的环境下探测原生function不可靠,因为core-js绕过了这类检测方法。尽管有多个请求,但是core-js维护者很清楚地声明:任何试图修复探测方法都会被阻止。因此,我们别无选择只能抛出错误。不幸的是,这样还是会影响那些依赖于core-js的包例如babel-polyfill
参数
value (*): 需要检查的值
返回值
(boolean): 如果是原生function返回true,否则false
例子
_.isNative(Array.prototype.push); // => true _.isNative(_); // => false
源代码
/** * lodash (Custom Build) <https://lodash.com/> * Build: `lodash modularize exports="npm" -o ./` * Copyright jQuery Foundation and other contributors <https://jquery.org/> * Released under MIT license <https://lodash.com/license> * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE> * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors */ /** `Object#toString` result references. */ var funcTag = '[object Function]', genTag = '[object GeneratorFunction]'; /** * Used to match `RegExp` * [syntax characters](http://ecma-international.org/ecma-262/7.0/#sec-patterns). */ var reRegExpChar = /[\\^$.*+?()[\]{}|]/g; /** Used to detect host constructors (Safari). */ var reIsHostCtor = /^\[object .+?Constructor\]$/; /** Detect free variable `global` from Node.js. */ var freeGlobal = typeof global == 'object' && global && global.Object === Object && global; /** Detect free variable `self`. */ var freeSelf = typeof self == 'object' && self && self.Object === Object && self; /** Used as a reference to the global object. */ var root = freeGlobal || freeSelf || Function('return this')(); /** * Checks if `value` is a host object in IE < 9. * * @private * @param {*} value The value to check. * @returns {boolean} Returns `true` if `value` is a host object, else `false`. */ function isHostObject(value) { // Many host objects are `Object` objects that can coerce to strings // despite having improperly defined `toString` methods. var result = false; if (value != null && typeof value.toString != 'function') { try { result = !!(value + ''); } catch (e) {} } return result; } /** Used for built-in method references. */ var funcProto = Function.prototype, objectProto = Object.prototype; /** Used to detect overreaching core-js shims. */ var coreJsData = root['__core-js_shared__']; /** Used to detect methods masquerading as native. */ var maskSrcKey = (function() { var uid = /[^.]+$/.exec(coreJsData && coreJsData.keys && coreJsData.keys.IE_PROTO || ''); return uid ? ('Symbol(src)_1.' + uid) : ''; }()); /** Used to resolve the decompiled source of functions. */ var funcToString = funcProto.toString; /** Used to check objects for own properties. */ var hasOwnProperty = objectProto.hasOwnProperty; /** * Used to resolve the * [`toStringTag`](http://ecma-international.org/ecma-262/7.0/#sec-object.prototype.tostring) * of values. */ var objectToString = objectProto.toString; /** Used to detect if a method is native. */ var reIsNative = RegExp('^' + funcToString.call(hasOwnProperty).replace(reRegExpChar, '\\$&') .replace(/hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g, '$1.*?') + '$' ); /** * The base implementation of `_.isNative` without bad shim checks. * * @private * @param {*} value The value to check. * @returns {boolean} Returns `true` if `value` is a native function, * else `false`. */ //_.isNative的基础实现 function baseIsNative(value) { if (!isObject(value) || isMasked(value)) { return false; } var pattern = (isFunction(value) || isHostObject(value)) ? reIsNative : reIsHostCtor; return pattern.test(toSource(value)); } /** * Checks if `func` has its source masked. * * @private * @param {Function} func The function to check. * @returns {boolean} Returns `true` if `func` is masked, else `false`. */ //检查一个函数是否隐藏了源码 function isMasked(func) { return !!maskSrcKey && (maskSrcKey in func); } /** * Checks if `func` is capable of being masked. * * @private * @param {*} value The value to check. * @returns {boolean} Returns `true` if `func` is maskable, else `false`. */ //检查是否func会被隐蔽,core-js造成的 var isMaskable = coreJsData ? isFunction : stubFalse; /** * Converts `func` to its source code. * * @private * @param {Function} func The function to process. * @returns {string} Returns the source code. */ //将函数转换成源码字符串 function toSource(func) { if (func != null) { try { return funcToString.call(func); } catch (e) {} try { return (func + ''); } catch (e) {} } return ''; } /** * Checks if `value` is classified as a `Function` object. * * @static * @memberOf _ * @since 0.1.0 * @category Lang * @param {*} value The value to check. * @returns {boolean} Returns `true` if `value` is a function, else `false`. * @example * * _.isFunction(_); * // => true * * _.isFunction(/abc/); * // => false */ //判断一个值是否给归类为function对象 function isFunction(value) { // The use of `Object#toString` avoids issues with the `typeof` operator // in Safari 8-9 which returns 'object' for typed array and other constructors. var tag = isObject(value) ? objectToString.call(value) : ''; return tag == funcTag || tag == genTag; } /** * Checks if `value` is the * [language type](http://www.ecma-international.org/ecma-262/7.0/#sec-ecmascript-language-types) * of `Object`. (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`) * * @static * @memberOf _ * @since 0.1.0 * @category Lang * @param {*} value The value to check. * @returns {boolean} Returns `true` if `value` is an object, else `false`. * @example * * _.isObject({}); * // => true * * _.isObject([1, 2, 3]); * // => true * * _.isObject(_.noop); * // => true * * _.isObject(null); * // => false */ function isObject(value) { var type = typeof value; return !!value && (type == 'object' || type == 'function'); } /** * Checks if `value` is a pristine native function. * * **Note:** This method can't reliably detect native functions in the presence * of the core-js package because core-js circumvents this kind of detection. * Despite multiple requests, the core-js maintainer has made it clear: any * attempt to fix the detection will be obstructed. As a result, we're left * with little choice but to throw an error. Unfortunately, this also affects * packages, like [babel-polyfill](https://www.npmjs.com/package/babel-polyfill), * which rely on core-js. * * @static * @memberOf _ * @since 3.0.0 * @category Lang * @param {*} value The value to check. * @returns {boolean} Returns `true` if `value` is a native function, * else `false`. * @example * * _.isNative(Array.prototype.push); * // => true * * _.isNative(_); * // => false */ //检查一个值是否是原生function //注意:这个方法在core-js包的环境下探测原生function不可靠,因为core-js绕过了这类检测方法。尽管有多个请求,但是core-js维护者很清楚地声明:任何试图修复探测方法都会被阻止。因此,我们别无选择只能抛出错误。不幸的是,这样还是会影响那些依赖于core-js的包例如babel-polyfill function isNative(value) { if (isMaskable(value)) { throw new Error('This method is not supported with core-js. Try https://github.com/es-shims.'); } return baseIsNative(value); } /** * This method returns `false`. * * @static * @memberOf _ * @since 4.13.0 * @category Util * @returns {boolean} Returns `false`. * @example * * _.times(2, _.stubFalse); * // => [false, false] */ //返回false function stubFalse() { return false; } module.exports = isNative;